Gas analysis method and apparatus



GAS .ANALYS IS METHOD AND APPARATUS Filed Dec. 31,1958

llll'llllll 5 OXYGEN ANALYZER 5 Fig.3.

-76' v FLgz'2. 1f 64 78 so I I -l l IA! i 54 6'6' Invenfior.

Patented Oct. 28, 1941 UNITED STATES PATENT OFFICE GAS ANALYSIS METHOD AND APPARATUS Wilfred R. Bendy, Seattle, Wash. Application December 31, 1938, Serial No. 248,760

9 Claims.

My invention relates to the analysis of gases and more particularly to the quantitative measurement of excesses and deficiencies of oxygen in flue gases such as are produced by kilns and combustion furnaces.

The economy of combustion operations depends greatly upon close adjustment of the relationship of combustion air to fuel. A well known method of determining the relationship is by analyzing the flue gases to determine-the amounts of uncombined oxygen and of combustible gases which are present. Continuously operating gas analyzers which measure the amount of combustible gases in flue gases are well known. Gas analyzers which measure the amount of oxygen in flue gases are known also.

The presence in flue gases of oxygen without combustible gases indicates an excess of 'combustion air. The presence in flue gases of combustible gases without oxygen indicates a deficiency of combustion air. When oxygen and combustible gases are both present in flue gases, the excess of one over the other, having regard to their combining proportions, is the indicative factor which may be termed the oxygen balance.

Flue gases may contain various combustible constituents among which carbon monoxide, hydrogen, and methane are selected for purposes of illustration. The reactions which take place when the aforesaid combustible gases combine with oxygen are expressed by the following equations:

An important object of the invention is to pro-,

vide method and means whereby excesses of combustible gases and excesses of oxygen in gases of-varying composition are measured quantitatively in one single-component analyzer.

"Anotherobject of the invention is to provide Insofar as thenovel means for measuring excesses and deficiencies of oxygen in flue gases by the position of a. single pointer on a single scale.

Another object of the invention is to measure mixed combustible constituents of gases in terms of the sum of their respective volumes of combination with oxygen.

Another object of the invention is to provide method and means whereby an excess of combustible constituents of gases is measured in terms of a deficiency of oxygen.

Another object of the invention is to provide means .for measuring excesses of combustible gases in oxygen analyzers of known types.

Other objects and advantages of the invention may be understood by reference to the following description and claims, together with the drawing, in which:

Fig. 1 shows diagrammatically apparatus for measuring excesses and deficiencies of oxygen in gases.

Fig. 2 is an enlarged view of the indicating pointer and scale of the oxygen analyzer shown in Fig. 1.

Fig. 3 shows a portion of a travelling record chart used with the oxygen analyzer.

with an inlet conduit I 2 adapted to receive a sample of gases, such as flue gases, from a suitable source. having a branch I6 leading to a pressure relief device l8 which functions to maintain a constant pressure on the flue gases in conduit [4. A pump 20 is provided with an inlet conduit 22 adapted to receive oxygen from a suitable source, and with an outlet conduit 24. As hereinafter described, said oxygen may be associated with inert gases in the form of air. a branch 26 leading to a pressure relief device 28 which functions to maintain a constant pressure on the oxygen in conduit 24.

A water bath 3.0 surrounds conduits I4, 24 in a position downstream from branches I6, 26

and functions to equalize the temperatures of the flue gases and oxygen which pass through said conduits. Orifices 34, 36 are positioned within said conduits downstream from the points of entry of conduits I4, 24 into water bath 30 and serve to regulate the respective amounts of flue gases and oxygen which pass therethrough into conduits 38, 40 which are connected jointly to conduit 42. The regulated streams of flue gas and oxygen are united and mixed within conduit 42.

The means so far disclosed have as object, the

Pump 10 has an outlet conduit l4,

Conduit 24 has.

addition of a measured amount of oxygen to a measured amount of flue gases in such manner that the mixture thus formed contains a fixed proportion of added oxygen. Air contains a substantially constant proportion of oxygen mixed with inert gases and may .be added to the flue gases instead of oxygen through orifice 36 to form a mixture containing a fixed proportion of added oxygen. Orifices 34, 36 are proportioned so that suificient oxygen is mixed with the flue gases to combine with the maximum amount of combustible gases which may be contained therein.

Mounted in conduit 42 is a combustion chamber 44, heated by electric coils 46, or other suitable means. Within combustion chamber 44 is a catalyst 48 which may be composed of palladium sponge, or of palladiumized asbestos, or of platinum gauze, or of platinized silica. or the like. Within combustion chamber 44, any combustible gases in the flue gases are caused to combine with the oxygen added through orifice 36 or with oxygen which may be contained in the flue gases. Some types of combustible gases may be completely combined with oxygen by the agency of heat alone, in which cases the catalyst 48 may be omitted.

The resulting mixture issues from combustion chamber 44 and passes through conduit 56 to oxygen analyzer 52, which has awaste outlet 58. Conduit 56 also serves to cool the mixture passing from combustion chamber 44. to oxygen analyzer 52. Oxygen analyzer 52 is provided with an indicating scale 54 and a pointer 56, which indicates the proportion of oxygen contained in the mixture after passing through combustion chamber 44'. Oxygen analyzer 52 may be of any one of several known types, such as continuously operating volumetric absorption analyzers, thermal conductivity analyzers, catalytic cell analyzers, or gas density analyzers. The functioning means of oxygen analyzer 52 are not described herein because they form no part of the present invention except insofar as the scale 54 and the pointer 56 indicate the proportion of oxygen in the mixture after passing. through combustion chamber 44.

Referring to Fig. 2, line 66 is the zero line on scale 54 of oxygen analyzer. 52. When pointer 56 stands at line 66', it indicates that the mixture received by oxygen analyzer 52 contains zero oxygen. Lines 62, 64, 66 indicate proportions of oxygen in the mixture greater than zero. When the flue gases are neutral in regard. to excessesof oxygen or of combustible gases, pointer 56 stands at line 64. and indicates the proportion of oxygen added to the flue gases. When the compositionv of the flue gases changes so that they contain an excess of combustible gases, a portion. of the oxygen derived from orifice 36 combines with the combustible gases in combustion chamber 44, causing the mixture to contain less oxygen than when the flue gases were neutral and causing pointer 56 to assume a new position, such as at line 62. The difference between the scale reading at line 64 and the scale reading at line 62' indicates quantitatively a deficiency of oxygen in the flue gases. When the flue gases contain an excess of oxygen, the mixture contains more oxygen than when the flue gases are neutral, causing pointer 56 to move to a new position such as at line 66. The difference between the scale reading at line 66 and the scale reading at line 64 indicates quantitatively an excess of oxygen in the flue gases.

Inorder that scale 54- may read directly excesses and deficiencies of oxygen in the flue gases, line 64 is designated as a datum line corresponding to neutral flue gases. The position of line 64 on scale 54 may be calculated from the sizes of orifices 34, 36, or it may be determined by observing the position of pointer 56 when flue gases of known neutral composition are supplied to pump I0. Said position may be varied by changing the proportions of orifices 34, 36. All positions of pointer 56 to the left of line 6-4 indicate excesses of combustible gases which, as hereinbefore explained, may be expressed in terms of deficiencies of oxygen. All positions of pointer 56 to the right of line 64 indicate excesses of oxygen in the flue gases.

Scale 54 may be calibrated to read percentage volumes of excesses and deficiencies of oxygen in the flue gases. For an average composition of flue gases, scale 54 may be calibrated also with substantial accuracy in terms of excesses, and deficiencies of combustion air. in relation to fuel used in the combustion furnace from which the fiue gases are. derived.

Referring particularly to Fig. 3, 68 is a portion of a travelling chart on which are recorded the successive positions of pointer 56 by means of a curve having portions 12,14, 16, 18. Line 16 is a datumline-corresponding to datum line 64 on scale 54, both said datum lines corresponding to neutral flue gases. Portions of the curve to the right of line 16,. such as 12, 16, quantitatively record excesses of oxygen in the flue gases. Portions of the curve to' the left of line 10, such as 14, I8, quantitatively record deficiencies of oxygen in the flue gases.

Certain known types of oxygen analyzers function in part through the agency of combustion chambers similar to combustion chamber 44 hereinbefore described. When oxygen analyzers of said types are used in conjunction with the invention, the combustion operation may be carried out solely within saidv oxygen analyzer Without departing from the spirit of the invention.

It will be apparent to those familiar with the art that means other than those described may be used. in carrying out the principles of the in- Vention. Other means for proportioning and adding oxygen to the sample gases may be substituted. for those shown in Fig. 1. Combustion of any combustible constituents of the sample gases may be effected by; the action of. heat, or by the action of a heated catalyst, or by means of a high-tension electric discharge. Accordingly, I do not wish to be limited to the means de- 1 scribed herein by way of illustration.

I claim:

1. In a combustion process, the method of determining the deviation from. the theoretical combustion ratio of. oxygen to fuel, which com.- prises: adding to flue gases, resulting from said process a constant proportion of oxygen at least as large as the maximum deviation. to be. measured in the'direction ofoxygen deficiency, thereby forming a mixture having. a fixed proportion of added oxygen; subjecting said mixture to conditions effecting combustion of any combustible gases present; and thereafter measuring the proportion of oxygen in the mixture relative to said fixed proportionof added oxygen,

2. In a combustion process, the method of determining the deviation from the theoretical combustion ratio of oxygen to fuel which comprises: mixing a stream of oxygen of constant quantity with a. stream of said gases of constant quantity to form a mixture having a constant proportion of added oxygen, the added Oxygen content thus obtained being not less than the maximum deficiency in oxygen balance which is to be measured; passing said mixture through a combustion chamber adapted to inducecombustion of any combustible gases; and thereafter measuring the proportion of oxygen in said mixture relative to said constant proportion of added oxygen.

3. Apparatus for analyzing gases comprising, in combination: means adding oxygen to said gases; means proportioning said oxygen to said gases to give a mixture containing a fixed proportion of added oxygen; a combustion chamber; means passing said mixture through said combustion chamber; an oxygen analyzer measuring the proportion of oxygen in said mixture; and a conduit conducting said mixture from said combustion chamber to said oxygen analyzer.

4. In apparatus for analyzing gases, the combination of: means forming a stream of said gases; a device adding a constant proportion of oxygen to said stream to form a mixture; means effecting combustion of any combustible gases present in said mixture; and means measuring the oxygen content of said mixture subsequent to said combustion.

5. The method of measuring deviations of oxygen content in gases from the amount of oxygen required for perfect combustion of combustible constituents of said gases, which come prises: mixing a quantity of oxygen with a quantity of said gases; proportioning said quantities to give a mixture having a fixed proportion of added oxygen, the added content of oxygen thus obtained being not less than the maximum deviation which is to be measured in the direction of oxygen deficiency; subjecting said mixture to conditions favorable to combustion of said combustible constituents; and thereafter measuring the proportion of oxygen in the mixture relative to said fixed proportionof added oxygen.

6. The method of measuring a deficiency of oxygen in gases which contain combustible constituents and which may also contain oxygen,

rwhich comprises: adding a measured volume of 1 oxygen to a measured volume of said gases;

proportioning said volumes so as to give a mixture having a fixed proportion of added oxygen, the total content of oxygen thus obtained being at least suflicient for complete combustion of said gases; subjecting said mixture to conditions producing combustion of said combustible constituents; and measuring any reduction in proportion of oxygen in said mixture relative to said fixed proportion of added oxygen. 7

7. Apparatus for analyzing a mixture of gases comprising, in combination: means for adding oxygen to the mixture "of gases so that said oxygen will constitute a known proportion of said mixture; a combustion chamber; means for passing said mixture including said added oxygen into said combustion chamber; means in said combustion chamber for effecting combustion of any combustible gases present in said mixture; and means for measuring the oxygen content of said mixture subsequent to said combustion.

8. A combination as provided for in claim '7 in which the means for measuring oxygen content is an oxygen analyzer including a scale having positive and negative values, said positive values measuring excesses of oxygen over that quantity required for perfect combustion of combustible gases in said mixture, and said negative values measuring deficiencies of oxygen below that quantity required for perfect combustion of combustible gases in said mixture, said negative values not exceeding the amount of oxygen initially added to said mixture.

9. A combination as provided for in claim 7 in which the means for measuring oxygen content is an oxygen analyzer including a scale having a datum thereon corresponding to said known proportion of oxygen initially added to said mixture, said scale extending on both sides of said datum.

WILFRED R. BENDY. 

